This invention relates to multifilament polyester yarns and particularly to improved multifilament polyethylene terephthalate yarns for industrial uses. More particularly, it relates to an improved multifilament polyethylene terephthalate yarn and a new fiber finishing process for polyethylene terephthalate yarns in which novel fiber finish compositions are applied to said yarns.
Many fiber finish compositions are known. Some are quite specific in composition and relate to specific type fibers. Small changes in fiber finish composition frequently result in tremendous improvements not only in processing but also in end use of the fiber.
Polyester industrial yarn finishes generally comprise a combination of a lubricant, an antistat, and several emulsifiers. For example, U.S. Pat. No. 3,672,977 discloses an improved polyester industrial yarn which is produced by first treating the yarn with a spin finish comprising hexadecyl stearate, refined coconut oil, ethoxylated tallow amine, ethoxylated lauryl alcohol, sodium salt of alkylarylsulfonate, dinonyl-sodium-sulfosuccinate, 4,4'-thio-bis-(3-methyl-6-tert-butylphenol) and white mineral oil, and then treating the yarn with an overfinish comprising glycerol monooleate, decaglycerol tetraoleate, ethoxylated tall oil fatty acids, sulfated glycerol trioleate, ethoxylated tallow amine and hexadecyl stearate. Although the process and product of this patent are certainly an important improvement in this art, research in this field has continued in an effort to further improve the yarn, and in particular to produce a yarn suitable for making tire cord which gives improved performance in tires and which does not turn yellow on exposure to light.